PETROPHYSICAL CHARACTERIZATION OF A MISSISSIPPIAN CORE INTERVAL FROM MCPHERSON COUNTY, CENTRAL KANSAS

Throughout the Mid-Continent region of the United States, Mississippian aged rocks are known to be prolific hydrocarbon reservoirs with both complex sedimentary and structural facies. Difficulties in accessing reservoir quality exist in these rocks due to heterogeneity in depositional processes, diagenetic controls, as well as, variability in depositional processes and conditions. Approximately 80 feet of Mississippian (Osagean – Meramecian) core was recovered from a well in McPherson County, Kansas. The upper 30 feet (between 2,916 ft and 2, 946 ft below ground level) of core was analyzed at one-foot intervals for porosity, permeability, oil and water saturation, grain density and lithology. Macroscopic and microscopic observations were conducted to determine textual characteristics, rock fabric, mineralogical and matrix properties to complete a detailed facies description. Lithologies of the studied interval include units of mudstone to packstone, dolomite, chert, tripolite and some brecciated intervals. Macroscopic observations in the studied interval show a combination of interparticle, intraparticle, fracture and vuggy porosity. Analysis of the interval shows average total porosity values of 23.8% with grain densities ranging from 2.62 to 2.80 g/cm³ and permeability ranges of Kmax 0.008 to 50.3 md, K90 0.004 to 39.1 md, Kvert 0.001 to 16.8 md. The average oil saturation for this interval was 2.5% and average water saturation was 88.6%. Observations and numerical values from the core interval were compared to the same interval on several well logs. This was to determine if the core observations and numerical values were correalateable to well log values. Preliminary results suggest that this interval was deposited in a neritic subtidal marine carbonate ramp system with meteoric water influx after deposition. The high porosity is mostly due to secondary diagenetic and deformational processes that have significantly enhanced permeability.